Formed metal workpieces often have a shaft or axle with a first portion having splines formed therein and a second portion which is threaded. For example, universal joints for vehicle drives conventionally include a joint member having four round surfaces of cylindrical shapes that are coaxial about a central axis of the joint member and have different diameters. The largest round surface is utilized with a seal to provide sealing of the joint, while the next largest round surface supports a bearing that mounts the joint. Both of the two smaller round surfaces are sequentially formed with projections, the larger one with splines utilized to rotatively couple the joint and the smaller one with a thread used in securing the joint in position.
A cooperable pair of moveable tools has been utilized to cold form noncylindrical workpieces as disclosed in the U.S. Pat. Nos. 4,192,292 to Simonds, issued Jan. 14, 1980 and 4,469,342 to Simonds, issued Feb. 24, 1981; 1,446,447 to Bingham, issued Feb. 27, 1923; 3,044,332 to Siebol, issued July 17, 1962; 3,466,918 to Marcovitch, issued Sept. 16, 1969; 3,498,095 to Marcovitch, issued Mar. 3, 1970; and 3,503,237 to Marcovitch, issued Mar. 31, 1970. The U.S. Pat. No. 2,825,251 to Raider issued July 19, 1952 discloses a pair of tools used to perform forming by holding one of the tools stationary and moving the other one with the workpiece between the two tools. The U.S. Pat. No. 65,575 to Loughran issued May 23, 1899 discloses a pair of straight tools that are moved rectilinearly to cold form a workpiece having a single cylindrical surface of a round shape.
Several problems are presented in forming a workpiece having a shaft with two portions of different diameters using prior art methods and assemblies. A blank may be formed including a cupped shaped portion and the shaft portion extending therefrom having three portions with different diameters, each portion having a substantially round cross section. The copending U.S. patent application to applicant Ser. No. 458,325, filed Jan. 17, 1983, discloses a method for cold sizing such a workpiece. Basically, the method is performed by mounting the workpiece for rotation about its central axis between a pair of die assemblies. Each of the die assemblies utilized include a plurality of dies having different sizing surfaces that extend parallel to the central axis of the workpiece respectively in alignment with the round surfaces of the workpiece. There is movement of the die assemblies in opposite directions as each engages the sizing surfaces of the dies with the round surfaces of the workpiece as the workpiece rotates about its central axis such that the sizing surfaces pressure size the round surfaces of the workpiece. In performing the method, it is also possible to continue the movement of the die assemblies in order to engage forming projections on the trailing end of one die of each die assembly with the aligned round surface of the workpiece to thereby form projections on this aligned round surface of the workpiece. Such projection forming can be utilized to provide splines on one of the round surfaces and can also be utilized to subsequently provide a helical thread on the other round surface of the workpiece. It is noted in the aforementioned application that only one round surface of the workpiece can be formed with projections at any given time due to the fact the the round surfaces have different speeds of circumferential movement for any given rate of the workpiece rotation and the die assemblies can each only have a single speed at any given time due to their meshed relationship with the workpiece at the projections being formed. Any attempt to simultaneously roll the spline and thread would result in unacceptable torsional stresses in the shaft causing breakage. The instant invention is directed to this problem and provides means for simultaneously forming the splines on one portion of a shaft and a thread in a second portion in a single pass wherein the two portions have different cross sectional diameters.